density
number of individuals in a population in an area or volume; size of a population in a given area or volume (number/area )
mortality
death rate, generally expressed as the number of individuals dying per unit of time per unit of population (deaths/year/1000 people)
natality
birth rate, generally expressed as the number of births per unit of time per unit of population (births/year/1000 people)
immigration
the movement of individuals into an area
emigration
the movement of individuals out of an area
biotic potential
the maximum growth rate of a population under ideal conditions
carrying capacity
the maximum number of individuals of a certain species that a given environment can support over extended periods of time without doing lasting damage to the environment itself
steady state
condition reached by a population where the density of the population remains relatively constant over extended periods
density dependent factors
factors affecting population growth which depend upon the number of individuals in the population to exert their effect, becoming more forceful with increasing density
density independent factors
factors affecting population growth that are not dependent upon the number of individuals in the population
density dependent factors (examples)
competition-when use of limited resource by one individual reduces its availability to another
interspecific interactions- different species (between)
intraspecific interactions- same species (within)
disease- spread of contagious pathogens
pollution-undesirable change to environment
intrinsic mechanisms-psychological and physiological responses
density independent factors(examples)
climatic conditions-temperature extremes, drought, flood, pollution
human population growth
human population growth curve over the past 200-300 years we see a sharp increase in birth rate > death rate
coincided with several advancements:
industrial revolution
agriculture
medical
age distribution
percentage of individuals in various age groups in a population
human population statistics
population density-number of humans per area
infant mortality-number of children born who don't survive to age of 1
total fertility rate- average # of children born to women in a population
age distribution- percentage of people in different categories
birth rate (world as of 2022)- Br: 17/1000/yr dr: 8/1000/yr
annual rate of natural increase (RNI)
RNI= BR-DR
17/1000-8/1000=9/1000 or 0.9%
doubling time
how many years it will take a population to double size at its current growth rate
rule of 70 or 70/RNI
sustainability
live in such a way as to maintain earth's systems and its natural resources for future generations
ecological footprint
measure of the impact of humans on earth
the area of land to produce resources and dispose of waste
consumption of resources X population per person
Current average us footprint 5.1 ha/person
to live sustainably need 1.7 ha/person
community ecology
communities are all populations in a given area (focus on interactions among species)
competition
use of similar resources
pop 1: negative
pop 2: negative
mutualism
symbiosis between species
pop1: positive
pop2: positive
predation
predator feeding on prey
pop 1: Predator positive
pop 2: prey negative
herbivory
eating plants
herbivore positive
plant negative
parasite/pathogen
parasite live in or on host
parasite positive
host negative
pathogen disease causing organism
pathogen postive
host negative
producers
autotrophs - plants some bacteria
consumers
heterotrophs-animals fungi some bacteria
primary consumers
eat producers
secondary consumers
eat primary consumers
tertiary consumers
eat secondary consumers
decomposers
bacteria and fungi, breakdown large organic molecules into smaller parts
food chain
linear series of foods and feeders
food web
a grouping and intermeshing of more than one food chain, complex interconnections of many food chains
herbivore
eat plants - primary consumer
carnivore
eat other animals - secondary/tertiary consumer
omnivore
organism that commonly eats both plant and animal
species diversity
number and abundance of species in a community
species richness
number of species
relative abundance
number of individuals of each species
communities with higher diversity
higher species ricchness-mroe species
higher species eveness - even abundance of species
keystone species
species with disproportionate effect on overall species diversity
toxicology
the effect of chemicals on humans and other organisms
mutagens
increase the rate of mutations -nuclear waste-uv radiation (sun burn)
carcinogens
cancer causing substances - cigarette smoke
teratogens
cause birth defects - alcohol
neurotoxins
disrupt the nervous system- pesticides DDT, heavy metals-> lead
endocrine disruptors
interfere with the endocrine system- pesticides atrazine, consumer products BPA
Insecticide advantages
many varities
easy to use
reasonable cost
usually temporarily effective
insecticide disadvantages
kill non target species
directly kill useful species
indirectly via biological magnification
carcinogenic
persist in environment
select for resistance
herbicide advantages
many varieties, easy to use, reasonable cost, usually temporary effective, no evidence of biological magnification
herbicide disadvantages
direct toxicity not well known for some microorganisms
weeds become resistant
endocrine disruptors
biological magnification
certain chemicals become concentrated as they move along the food chain
DDT is stored in fat cells not excreted tends to accumulate in organisms
lethal levels
causes death
bats&DDT
sublethal effects
some detrimental effect to organism or offspring
eggshell is thin -> affects reproduction of birds
endocrine distruption- feminization of frogs
importance of Silent Spring by Rachel Carson 1962
large scale pesticide use
brought issue to public attention
influenced environmental protection acts
environmental protection acts
clean air act 1969, clean water act 1977, toxic substances control act 1976, ban DDT in 1972
biological control
method of controlling pest species without harming non-target species
introduction of natural enemies of pests
sterilization of male insects
attractants- light sound
resistant crop varieties- genetic engineering
integrated pest management
monitor fields closely
early detection of outbreak
use small amount of pesticide (last resort)